1. Field of the Invention
The present invention relates generally to a call distribution method in a mobile switching system, and in particular, to a call distribution method for distributing location registration and mobile subscriber's outgoing call using a plurality of managed intelligence nodes (MINs) having a call server function in a mobile switching system.
2. Description of the Background Art
Generally, a mobile switching system performs location registration and call processing of a mobile subscriber in one mobile switching center (MSC). Thus, an increase in number of the mobile subscribers causes an overload of the system, making it difficult to provide a rapid service. Therefore, there has been a demand for an improved mobile switching system in which the mobile switching center performs only the switching function and processes various call processing functions including visitor location register (VLR) information by using a plurality of managed intelligence nodes (MINs) included therein.
The mobile switching center manages the routing of calls in a large service area. The mobile switching center is sometimes also called a mobile telephone switching office (MTSO). The mobile switching center may connect the cellular base stations and the mobiles to a public switched telephone network (PSTN). The public switched telephone network is a telephone network that has connections established when required. The telephone network is controlled by one or more entities to provide telephone service available to the public. Each mobile user communicates via radio with one of the base stations and may be switched to a number of base stations throughout a call as the mobile user moves through a service area. The base stations may have multiple transmitters and receivers to connect a call between the mobile user and a public telephone network. The base station links between the mobile user and the mobile switching center.
Generally, as an example, when a telephone call is placed to a mobile user, the mobile switching center dispatches the request to all base stations in the mobile telephone system. The mobile identification number is then communicated over all of the control channels of the mobile telephone system. The mobile identification number may be the mobile user's telephone number. The mobile user transmits a verification of the mobile identification number to the base station which then forwards the verification to the mobile switching center. The call is forwarded to the mobile user. The mobile switching center may make the proper adjustments in such items for example frequency, channel selection, transmission power, etc. As the call is in progress, the mobile switching center may perform a handoff which is the adjustment of the channel of the mobile unit and base stations so that the signal quality is maintained while the user or subscriber moves in and out of range of each base station. When a mobile unit originates a call, a call initiation request is sent having such information as the telephone number of the mobile unit, the serial number of the mobile unit, and the telephone number of the party being called. The mobile switching center validates the request and forwards the connection to the called party through the public switched telephone network (PSTN) and instructs the base station and mobile unit that the telephone connection may begin.
The mobile switching center may use databases such as the home location register (HLR), the visitor location register (VLR), and the authentication center (AUC) to update location and registration records for all subscribers in the network. A mobile subscriber becomes a roaming subscriber when it leaves the coverage area of the mobile switching center to which it was originally subscribed (home mobile switching center). To allow access to the public switched telephone is network to the roaming subscriber, the roaming subscriber is required to register with the mobile switching center in which the roaming subscriber presently resides. The mobile switching center used by the roaming subscriber can be called a visitor mobile switching center. Registration is a process where each roaming subscriber notifies the mobile switching center servicing the roaming subscriber of the presence of the roaming subscriber and the location. The registration is transferred to the home mobile switching center where the home location register is updated. The home register contains a list of all users along with information such as their mobile identification number who originally subscribed to the network in that particular region. The visitor location register (VLR) changes over time the list of users who have roamed into a particular area of the network. The mobile switching center updates the visitor location register by first determining that the users are roamers. Because billing rates for roaming may vary, it is important to verify the roaming mobile users. The mobile switching center can verify whether a user is a roaming subscriber by the mobile identification number of a user with the mobile identification numbers contained in the home location register.
Exemplars of the art are U.S. Pat. No. 5,841,854 issued to Schumacher et al. for Wireless Telephone Integration System and Method for Call Centers and Workgroups, U.S. Pat. No. 6,144,671 issued to Perinpanathan et al. for Call Redirection Methods in a Packet Based Communications Network, U.S. Pat. No. 5,915,212 issued to Przelomiec et al. for System and Method for Achieving Extended Radio Coverage and Additional Capacity Using Extended Frequency Bands, U.S. Pat. No. 5,400,390 issued to Salin for Method for Establishing an Inbound Call to the Mobile Telephone in a GSM Cellular Mobile Telephone Network, U.S. Pat. No. 5,428,665 issued to Lantto for Method of Managing Supplementary Service Procedures in Gsm/vlr Towards Hlr, U.S. Pat. No. 5,920,814 issued to Sawyer et al. for System and Method of Managing Temporary Mobile Station Identity (TMSI) Parameters in a Radio Telecommunications Network, U.S. Pat. No. 6,097,950 issued to Bertacchi for Method and System for Global Roaming in a Cellular Telecommunications System, U.S. Pat. No. 6,081,705 issued to Houde et al. for Cellular Telephone Network Support of International Mobile Station Identity (IMSI), U.S. Pat. No. 5,844,522 issued to Sheffer et al. for Mobile Telephone Location System and Method, U.S. Pat. No. 6,134,435 issued to Zicker et al. for Cellular Radiotelephone System with Remotely Programmed Mobile Stations, and U.S. Pat. No. 6,119,012 issued to Amirijoo for Method and System for Dynamically and Periodically Updating Mobile Station Location Data in a Telecommunications Network. I have found that the art does not show a method for performing rapid call distribution by distributing a signaling interfacing and switching function and a call control function in a mobile switching system.